The present invention relates to the field of intravascular balloon catheters. In particular, the present invention relates to an adaptor which is able to modify the performance of an intravascular balloon catheter to suit a variety of vascular conditions.
Intravascular balloon catheters have been effectively used to treat various maladies associated with the vascular system. For instance, angioplasty has gained wide acceptance as an efficient, effective and alternative method of removing undesirous restrictions caused by tissue growth or lesions on the inner walls of the blood vessels. Such tissue growth or lesions cause a narrowing of the blood vessels called a "stenosis," which severely restricts or limits the flow of blood.
In the most widely used form of angioplasty, a dilatation catheter, which has an inflatable balloon at its distal end, is carefully guided through the vascular system. This guiding process is arduous and time intensive. With the aid of fluoroscopy, a physician is able to position an uninflated balloon across the stenosis. The balloon, often made of a compliant material, is then inflated by applying fluid pressure through an inflation lumen of the catheter to the balloon. The radial size of a compliant balloon is a function of the inflation pressure supplied to the balloon. In other words, the greater the inflation pressure, the greater the radial size of the compliant balloon. This feature of a compliant balloon advantageously permits a physician to alter the inflation pressure (and hence the radial size of the balloon) to suit the size of the blood vessel in which the stenosis is located. Ideally, inflation of the balloon, within the balloon's working inflation pressure range, cracks and compresses the stenosis-causing lesion toward the artery wall to remove the constriction and re-establish acceptable blood flow through the artery.
Some physicians, however, prefer to use a dilatation catheter, under some circumstances, which has a balloon made of a relatively non-compliant material (i.e., a balloon which will retain a given radial size as inflation pressure is increased).
It is often desirable to keep the balloon inflated within the artery for relatively significant periods of time. One disadvantage of many dilatation catheters of the prior art is the complete occlusion of the blood vessel that results while the balloon is inflated. Prolonged complete blockage of a coronary artery results in discomfort to the patient and poses serious risk of damage to the tissue downstream from the occlusion which is deprived of oxygenated blood. These consequences limit the length of time the balloon can remain expanded within an artery to effectively re-open the artery.
Various means for providing passive perfusion of blood through or past the inflated balloon have been permanently incorporated into either the catheter shaft or the balloon. Examples of such perfusion catheters are found in the following prior art references: Baran et al. U.S. Pat. No. 4,423,725; Sahota U.S. Pat. No. 4,581,017; Hershenson U.S. Pat. No. 4,585,000; Horzewski et al. U.S. Pat. No. 4,771,777; Mueller et al U.S. Pat. 4,790,315; Songer et al. U.S. Pat. No. 4,892,519; Goldberger U.S. Pat. No. 4,909,252; Sogard et al. U.S. Pat. No. 4,944,745; Sahota U.S. Pat. No. 4,983,167; Boussignac et al. U.S. Pat. No. 5,000,734; Patel U.S. Pat. No. 5,000,743; Bonzel U.S. Pat. No. 5,002,531; and Sahota European Patent Application 0 246 998.
While perfusion catheters are capable of performing perfusion during balloon dilatation, certain drawbacks exist. For instance, the profile of perfusion catheters is generally considerably larger than that of an ordinary balloon dilatation catheter. The larger profile of perfusion catheters can inhibit and/or prohibit such a catheter from crossing a stenosis, especially when the stenosis is quite narrow. In addition, perfusion catheters known in the art are not capable of providing blood flow to side branches of the artery which occasionally are blocked by the inflated balloon. Finally, the need to use a perfusion catheter usually does not become apparent until after a relatively simple dilatation catheter has been used. Thus, in order to obtain perfusion capability with an intravascular catheter, the ordinary balloon dilatation catheter must be removed from the vascular system, and the arduous and time intensive task of rerouting a perfusion catheter within the vascular system must be undertaken. A replacement of a catheter such as this, under extreme circumstances, is not without adverse risks or consequences.
The ability to safely, successfully and efficiently perform dilatation of an occluded artery would be enhanced if only one relatively simple dilatation balloon catheter could be adapted to a variety of arterial conditions. Furthermore, the ability to perfuse past or to increase the burst pressure and strength of an ordinary, prepositioned dilatation balloon would save considerable economic cost, considerable time and potentially considerable discomfort to the patient.